Figure 1: Total energy and substitutive work in the US economy. The solid lines represent consumption of energy careers (primary energy, top curve) and productive consumption of energy (substitutive work, bottom curve). The dashed line depicts primary energy needed for work of production equipment, estimated directly on the basis of empirical data. Primary substitutive energy is also calculated (and depicted by symbol ) as a part of primary energy, which is anticorrelated with labour. All quantities are estimated in quads per year (). According to Figure 1 of .